1. Field of the Invention
The present invention relates to an image correction processing apparatus, an image correction processing method, a program, and a storage medium, for applying correction processing suited to respective areas such as a text area, photograph area, halftone dot area, and the like.
2. Description of the Related Art
A copying machine which optically scans a document image and prints a scanned image on a print medium such as a paper sheet or the like has been proposed. However, the edge of an image optically scanned by a scanner of a copying machine is blurrier than that of the original document image, and only an image with decreased sharpness is obtained when the scanned image is printed on a print medium intact. Also, upon applying an edge enhancing process to image data after scanning for the purpose of enhancement of the sharpness of a printed image, moiré generated in a halftone dot area is also enhanced. To prevent this problem, a technique using image area segmentation has been proposed. The image area segmentation is a technique which segments, e.g., scanned image data into two areas such as a text area and halftone dot area, and applies an edge enhancing process to the text area and a smoothing process to the halftone dot area to attain enhancement of sharpness and a reduction of moiré at the same time.
However, if a judgment error occurs in the image area segmentation, the smoothing process may be applied to a text area, and the edge enhancing process may be applied to a halftone dot area, thus deteriorating an image. Depending on the precision of the image area segmentation, for example, a part of a character may be judged as a text area, and the remaining part of the character may be judged as a halftone dot area. In this case, upon printing an actual character, switching of the edge enhancing and smoothing processes occurs. Such switching of the edge enhancing and smoothing processes considerably impairs image quality. In order to prevent this, the following techniques have been proposed.
The first proposed technique in the past is a technique that continuously sets an edge enhancing amount according to an edge amount (e.g., Japanese Patent No. 03099354). With the first technique disclosed in Japanese Patent No. 03099354, adaptive edge enhancement according to the edge amount can be applied, and image deterioration of a printed image can be reduced.
The second technique is a technique that adaptively sets an edge enhancing amount according to an edge amount, and disables the adaptive setting for a halftone dot area (e.g., Japanese Patent Laid-Open No. 2002-077623). With the second technique disclosed in Japanese Patent Laid-Open No. 2002-077623, adaptive edge enhancement according to the edge amount can be applied, and edge enhancement of the halftone dot area can be reduced.
The third technique is a technique that segments an image into multiple areas including a text area, photograph area, and halftone dot area according to the continuity and density difference of black pixels (e.g., Japanese Patent No. 03472094). With the third technique disclosed in Japanese Patent No. 03472094, more flexible image area segmentation can be implemented.
In case of the first technique disclosed in Japanese Patent No. 03099354, an edge enhancing amount is set focusing on an edge amount (changing amount). However, since a halftone dot area also has an edge in the same way as a text area, it may have the similar edge amount (changing amount) as the text area. At this time, a large edge enhancing amount is also set for the halftone dot area in the same way as the text area, and moiré is also enhanced.
In case of the second technique disclosed in Japanese Patent Laid-Open No. 2002-077623, an edge enhancing amount is adaptively set focusing on an edge amount (changing amount) as in the first technique. However, this technique also focuses on a halftone dot cycle (the number of changes), and disables the adaptive edge enhancing amount setting based on the halftone dot cycle (the number of changes). For this reason, edge enhancement on a halftone dot area can be stopped, thus reducing moiré enhancement. However, although the edge enhancing amount is adaptively set up to a certain number of changes in accordance with the edge amount, when the predetermined number of changes is reached, the adaptive edge enhancing amount setting is disabled irrespective of the edge amount. Therefore, switching of the processes occurs when the predetermined number of changes is reached, thus deteriorating a printed image.
Furthermore, in case of the third technique disclosed in Japanese Patent No. 03472094, the image area segmentation that utilizes the continuity and density difference of black pixels is performed. In this case, this technique focuses on a halftone dot cycle (the number of changes), since the changing amount of an image signal decreases with increasing continuity of black pixels. Also, this technique focuses on the edge amount (changing amount) since the density difference of black pixels is the changing amount of an image signal. Three or more values are set for both the number of changes and changing amount to segment into multiple areas including at least a text area, photograph area, and halftone dot area by image area segmentation, thus improving the segmentation precision. However, the third technique does not disclose adaptive segmentation according to the number of changes and changing amount, and adaptive application of process strengths. That is, application of the third technique alone cannot execute adaptive processes according to the number of changes or changing amount. Hence, switching of the processes occurs, which deteriorates a printed image.
None of the first to third techniques disclose any “example that uses a plurality of interacting correction processes although these processes have different purposes”. Therefore, none of these techniques discloses “adaptive application of process strengths of the plurality of interacting correction processes although these processes have different purposes”.
That is, in the “example that uses a plurality of interacting correction processes although these processes have different purposes”, application of the first and second techniques cannot cope with the “interacting” part, thus deterioration of a printed image occurs undesirably in specific combinations. Upon application of the third technique, the number of times of switching of correction processes increases with increasing number of correction processes, thus the number of places of occurrence of image deterioration on a printed image increases unwantedly.